Socket



Feb. 27, 1934. PEARSON 1,949,359

SOCKET Filed March 23, 1931 2 Sheets-Sheet 1 F'Qk. 27 21934. 1G. PEARSON 1,

SOCKET 1 Filed March 25, 1951 2 Sheets-Sheet 2' Patented Feb. 27, 1934 warren STATES PATENT OFFICE 1,949,359 sooka'r Application March 23, 1931. Serial No. 524,428

s Claims. (or. its-32's) My invention relates to sockets for mounting vacuum tubes or plug-in coils, and is more particularly concerned with the construction of the contacts for engaging the prongs or studs of a tube or of a plug-in coil and the like when the same is inserted into the socket.

In the copending application of Newton C. Schellenger, Serial No. 341,945, filed February 23, 1929, there is described a socket employing contact springs, each provided with a pair of edges disposed longitudinally of a corresponding prong or stud of a tube inserted in the socket, for making a pair of line contacts along the sides of the corresponding stud.

The present invention provides an improvement upon the form of contacts disclosed in the above mentioned copending application. The form of contact which I have invented has proven to be highly efficacious and reliable, not only for the initial insertion of the prong or stud into the socket but for an indefinite large number of repeated operations.

S0 nearly as I can determine, the chief virtue of this form of contact lies in the unusually high unit pressure which the contact affords, and in the fact that the high pressure is concentrated in one or more lines extending substantially parallel to the axis of the stud or prong. At the same time, no unusual strength of spring is required.

This unusually high unit pressure is attained,

by presenting a relatively sharp edge to the surface of the stud. The sharper the edge, i. e., the nearer a perfect line contact is secured, the greater; does the unit pressure become for a given strength of spring. This concentration of pressure is so high that the film of oxides and other materials deposited on the surface of the stud is broken. This action is assisted by the longitudinal motion of the stud along the contact when the tube or coil, bearing the stud, is inserted in the socket. At the same time the unit pressure upon the edge of the contact spring is equally high so that any film of oxide or the like deposited thereupon is also broken and likewise cut by the longitudinal motion of the stud against the socket. In certain prior structures, the pressure of the contact upon the stud is applied at an angle and tends to lift the tube out of engagement with the socket. This, of course, must be prevented. w

A contact of this type should therefore exhibit the following features: It should give sufficient pressure to secure a reliable contact; there should be considerable extent of contact; and the pressure should be applied so as to hold the contact stud securely in place under any circumstances arising in the course of the normal operation.

The contact as disclosed in the present case provides the above recited desirable features. In addition, it embodies a form which brings these features into play with greater assurance and certainty than is the case in prior structures.

Now, according to the present invention, I provide a resilient backing for the/contact spring which has a different law of resistance from that 7 of the single leaf spring. This reinforcing backing offers a compound action with progressively increasing resistance to the contact spring, thereby reinforcing the contact spring positively and adding to the unit pressure with which the edges so of the contact spring engage the stud or prong of a tube or of the corresponding member which is inserted in the socket.

In the preferred form I provide a backing spring disposed substantially centrally in back of the contact spring. When the contact spring is defiected it will be reinforced at its central part by the resilient backing spring. The reinforcing pressure will progressively increase as the contact spring is deflected against the pressure of the go backing spring.

This backing spring comprises, in one embodiment, a pair of resilient wings which are curved with their ends toward each other and thus form an open arch in back of the contact spring. The contact spring is disposed'in the path of the stud, and, when the stud is inserted through a guide opening in the supporting base, it will deflect the contact spring and carry the same back against the backing spring. The resilient curved wings of the backing spring will be flexed and the ends of the wings will abut. The wings will thus provide a yielding reinforcing force for the contact spring which will gradually increase as the wings are flexed. When the contact spring is carried back further, it will depress the wings and the same will be spread laterally, flatteningthe arch formed by the wings. This action will contribute toward a further increase of the reinforcing force.

The backing spring may be formed of the same a bracket having great rigidity in its frame or back portion and a relatively yielding front portion for engagement with the back of the contact spring.

The back of the bracket presents the strength of its metal edgewise and the front or engaging part thereof presents themetal flatwise in bending. This gives a rapid. increase in pressure of the backing spring as it is deflected. As mentioned previously, this increase may be further secured by permitting the flexible front ends which are curved transversely to engage each other end to end as the contact spring bends them back. This abutting of the ends of the backing spring during the action thereof causes a different law of resiliency to prevail because the further tendency to carry back the flexible parts of the backing spring will tend to bend the arch which these abutting ends form and thus involves not only the flexing of the flat ends of the backing spring but the spreading of the sides of the bracket body by flattening 'of the arch which these ends form. The structure and function of this particular embodiment of the backing spring and of other embodiments thereof cooperating with the contact spring will be fully understood from the detailed'description which is yet to follow. However, before presenting the detailed account of the invention, I will briefly state thesali'entfeatures and objectsso that the subsequent explanations may be better understood and appreciated.

One object of the invention relates to the provision of a resilient contact spring disposed in the path of a cylindrical contact stud and having relatively sharp edges for engaging the surface of the stud substantially parallel to the axis of the stud.

Another object is concerned with a contact spring for establishing connection with a slidable stud; and resilient reinforcing meansdisposed in back of said contact spring for applying progressively increasing pressure upon said contact spring in a direction substantially transversally to .the axisof said stud. q

A further object has to do with a contact spring having relatively sharp edges for longitudinal engagement with a cylindrical contact stud, and backing means disposed substantially centrally of said contact spring in back thereof, for reinforcing the pressure ofsaid edges upon said coritact stud. S

Still another object contact spring adapted to be deflected against said backing means when engaged by a contact stud, wherein said backing means comprises two cooperating resilient members for-resisting the comprising two curved wings adapted to abut responsive to being deflected by the pressure of the flexible Tree portion exerted thereupon, to form an arch which maybe spread responsive to further increased pressure exerted by the said flexib e 1 1. 6

.portion, to reinforce said flexible free contact porillustrated in the Figures 1 and 2;

is realized in the combination'of a resilient backing means for a resilient tion with rapidly increasing pressure.

The above statements recite only the salient features of the invention. Other features will be brought out as the description progresses.

Now, in order to acquaint others with my invention, I will describe the same with reference tothe accompanying drawings in which I have shown certain practical embodiments thereof. In these drawings:

Figure 1 is a top side view of a. completely assembled socket;

Figure 2 represents a bottom side view of the completely assembled socket;

Figure 3 illustrates a. partial cross sectional viewv through the socket, taken on line 3- -3 in Figure 2 and showing one of the contact springs and associated backing in side elevation;

Figure 4-is a detailed view similar to the view shown in Figure 3, with the contact spring engaging a stud or prong;

Figure S'shows an enlarged cross sectional view of the contact spring engaging the cooperating stud'and being reinforced by the backing means This section is taken on line 55 of Figure 4;

Figure 6' represents a perspective view of one embodiment of the novel contact spring and coopcrating backing spring made of one piece of stock. This embodiment is. employed in the assembly 'Figure 7 illustrates a cross sectional side view similar to the one in Figure 4, but showing a different embodiment of the contact spring and associated backing means;

Figure 8 represents a further modification of the contact spring and the associated backing spring in side elevation as attached to a' socket base;

Figure 9 is a further embodiment of the contact spring and cooperating backing spring, wherein the backing spring is a separate member and mounted in assembly with the contact spring;

Figures 10 and 11 illustrate a side view and a plan view, respectively, of the separate backing spring employed in the structure shown in Figwhich is employed in the assembly shownin the Figures 1 and 2 and particularly illustrated in perspective view in Figure 6. I

By referring to Figures 1-5, it will be seen that the socket comprises the insulating base 1, to which I attach the contact springs generally designated by the numerals 2, 3, 4 and 5. The contactspring which is used in the assembly shown in Figures 1 and 2 'may be formed in different ways as will be discussed later-on. In this particular embodiment I have shown a contact spring and associated backing formed of one piece of stock.

This embodiment is particularly illustrated in Figure 6, and before continuing the description of the -assemblies in Figures 1- and 2, I shall describe the Figure 6 in detail.

Referring now to Figure 6, the contact spring andassociated backing comprises a base portion designated by the numeral 6.v The contact spring portion is slotted at 'l and rises from this base portion at an angle, providing two parallel sharp edges for engagement with the cooperating stud with which contact is to be established. The slot is imiicated in Figure 6 by the numeral 7 and the body portions of the contact springs which form this slot 7 are indicated by the numerals 8 and 9. Two projections 10 and 11 are bent out from the base portion 6. These projections will engage corresponding holes in the base 1 of the socket when the spring is mounted thereon so that rotation of the spring relative to the socket base is prevented. The sides of the spring body are bent angularly to the base portion 6 so as to form two parallel sides as indicated by the reference numerals 12 and 13. From these sides 12 and 13 extend two wings 14 and 15 toward the front and the ends of these wings are curved toward each other in back of the slotted contact portion. A terminal 16 is formed at the other end of the contact and two holes 17 and 18 are provided for the attachment of the connecting wires. This terminal could obviously be formed in a different manner. It is preferably tinned in order to provide for the ready soldering of the connecting wires thereto. In the base portion 6 of the con tact is formed a suitable hole (not shown in Figure 6) for the attachment of the contact to the insulating base 1.

Such a contact and associated backing spring may be made of spring brass or bronze, although German silver or any other suitable material may be used. The contacts are blanked out by means of the usual blanking die in a form as is particularly shown in Figure 14. I have applied in Figure 14 primed reference numerals corresponding to the reference numerals applied in Figure 6 and referring to like parts. I

Accordingly, reference numeral 6' in Figure 14 denotes the base portion of the contact; numerals 8' and 9' denote the sides of the contact spring portion which is slotted as indicated at '7'. Numerals 10. and 11 indicate the projections which will be bent out from the base portion 6 in order to secure the contact member on the insulating support; 12' and 13 will form the sides of the backing or reinforcing spring cooperating with the slotted contact spring; 14 and 15 indicate the wings which will be curved toward each other at the front end in back of the contact spring; and 16' indicates the terminal portion having the holes 17' and 18. A hole 19 is shown in the base 6'. This hole, it will be recalled, is not shown in Figure 6 but is provided in the base portion 6' as shown in Figure 14 and serves the purpose of attaching the contact to the insulating base by means of a rivet and the like. The sides 12" and 13' will be bent along the dotted lines indicated at 20 and 21. The spring portion having the slot '7 will be bent along the dotted line shown at 22, and the projections 10 and 11 as well as the terminal portion 16 will be bent along the line indicated at 23.

Referring now again to the Figure 6 and assuming that the contact is mounted on the insulating base as shown in the Figures 1 and 2, the operation will be as follows: When a tube or the like is inserted into the socket, a prong or s ud of the tube will move longitudinally to the slot such as 7 of the corresponding contact springs and will come into sliding contact with the sharp edges of the slot. The contact spring is resilient. It lies in the path of the stud, and, when the stud is inserted, it will be deflected toward the wings 14 and 15 of the backing spring. When the sides 8 and 9 of the contact spring engage the curved front portions of the wings 14-15 of the backing spring the force of these backing springs will reinforce the resiliency of the contact spring. Oxide and other material deposited on the stud of the tube will be broken and a firm contact will be established as the stud is moved along the edges of the slot '7. The pressure which will be applied during this engagement of the stud with i the contact spring will gradually increase as the curved portions of the wings 14 and 15 are carried back.

It will be seen that the force exerted thus on the sides 12 and 13 of the backing frame will be rigidly opposed by these sides since the strength of the metal is presented edgewise while the front portions or the wings will yield since the strength of the metal is presented flatwise in bending. The edges of the curved wings 14 and 15 will abut and, at this moment, the reinforcing pressure will be increased. The curved portions of the wings 14 and 15 will now form an arch. This condition is particularly illustrated in Figure 5 which I will now explain.

As shown in Figure 5, the contact stud 24 has engaged the sharp edges 25 and 26 of the contact spring sides 8 and 9 and the latter have established contact with the curved front ends of the backing wings 14 and 15. These curved, front portions now form an arch, the edges being in abutment as shown. Now, when the slotted contact spring is carried back further by the pressure of the contact stud 24, the result is that the resilient curved wing portions will be spread as is indicated in Figure 5 by the numerals 27 and 28; This action will contribute toward a further increase of the reinforcing pressure of the backing portion of the contact relative to the contact portion thereof.

With the above description of the structure and the function if the contact as shown in Figure 6 in mind, the following detailed description of the socket assembly shown in Figures 1 and 2 will be easily understood.

Referring now again to these Figures 1 and 2, I have shown mounted on the insulating base 1 four contacts, generally designated by numerals 2, 3, 4 and 5, respectively. Each of these contacts-may be of the form as shown in Figure 6. The slotted contact portions are-shown adjacent to the holes 29, 30, 31 and 32. The holes 29 and 30 are of larger diameter than the holes 31 and 32 which is in accordance with the practice of providing on a vacuum tube studs or prongs of larger and smaller diameters for the purpose of locating the tubes exactly as is demanded by the circuit. Each of the contacts is shown attached to the insulating base 1 by means of the rivets designated by the numerals 33, 34, 35 and 36, respecfiively. These rivets may be solid rivets or eyelets. The mounting of each of the springs against rotation on the insulating base 1 by means of the projections-such as 10 and 11 (Figure 6) is seen clearly in these figures. For example, the projections 37 and 38 of the contact 2 extend through corresponding holes on the insulating base 1 thus holding the contact against rotation relative to the rivet or eyelet 33. Likewise, the projections 43 and 42 on the contact 5 look this contact against rotation. Holes such as 39 and 40 are provided for moun ing the insulating base as desired. The insulating base may be made of phenol-condensation product, such as Bakelite or Mioarta-plate, although other suitable insulating materials may be substituted.

opening tangential to the outward edges of the stud guide holes for assisting in the guiding of the studs into registration with their respective holes. This is particularly described in the aforementioned copending application and details thereof may be had from examining the same.

In Figure 3, which is taken on line 33 of Figure 2, there is shown a side elevation of the contact 5 and cooperating backing spring. Referring to this Figure 3 and also to the Figure 2, it will be seen that the contact is mounted on the insulating base 1 by means of the rivet or eyelet 36. The guide hole for the stud is indicated in dotted lines by the numeral 32. Now, in describing this particular spring in detail and .its relation to the mounting hole 32 of the stud, it will be seen that the slotted spring portion having the sides 8 and 9 extends into the path of the stud which will be projected through the guide hole 32. The backing wings 14 and 15 are shown in back of the slotted contact spring centrally thereof. The spring is held against rotation relative to the rivet or eyelet 36 on the mounting plate 1 by means of the projections 42 and 43 which extend into corresponding holes on the insulating plate 1. The terminal 44 slants angularly from the base of the spring as shown.

Figure 4 represents a further stage of the operation of the novel spring. The stud 24 of the tube or plug-in coil has been inserted and is shown in contact with the slot 45 of the contact. The spring portions 8 and 9 were carried back during the longitudinal movement of the stud 24 along the sharp edges provided by the slot 45 and, in flexing backwardly, have established contact with the curved ends of the backing wings 14 and 15. These wings have exerted increasing pressure upon being deflected, and, during a certain stage of this operation, the ends of the wings 14 and 15 have met and formed an arch. A further carrying back of the slotted contact spring portion causes a spreading of the arch which contributes towards presenting a further resistance and increased pressure against the action of the contact spring portion.

The condition existing after the stud 24 is completely inserted and in full contact with the contact spring portion is particularly illustrated in Figure 5 which is taken along the line 55 of Figure 4 and which was discussed in detail previously.

I desire to call particular attention to the position of the contact stud 24 relative to the sharp edges 25 and 26 of the slot 45 of the contact spring as shown in Figure 5. These edges could obviously be formed differently. For example, sharp edges corresponding to those presented by the slot 45 may be formed by striking out parallel ears or lugs from the body of the spring, said ears or lugs extending longitudinally of the body of the spring, thereby providing sharp edges outside of the plane of the front surface of the sides 8 and 9. Such ears or lugs may be struck from the edge of a central slot or from the edges of two parallel slots. Whether the slot and the contact edges are formed according to the preferred method as shown or according to the optiona1 method above described is fundamentally immaterial. The stud will engage the edges of the slot and these edges will form line contacts along the surface of the stud and substantially parallel to the axis of the stud. When the stud is inserted, it will slide with its surface along the edges 25 and 26, initially against the pressure of the contact portion and, as the same is carried back, against the progressively increasing pressure provided by the action of the backing' wings.

I have shown in the above described embodiment that the slots in the contacts are of a certain width. Obviously, the slots may be made as desired, wider or narrower, in accordance with the diameter of the corresponding contact studs.

The holes for the studs represent a guide means therefor, and the contact portions are disposed in the paths of the respective studs as shown and described.

It is believed that the above description conveys a clear understanding of the functions and of the structure of this particular embodiment of the novel contact and associated backing spring as illustrated in the Figures 1 to 6, inclusive and in the Figure 14.

Referring now to the Figure 7, I have shown in this figure a modification which will be easily understood with the previous description in mind. The figure shows a partial section through an insulating plate such as the insulating plate 1 discussed in connection with the Figures 1 and 2, and corresponds to the detail shown for example in the Figure 4. The insulating plate is designated in Figure 7 by the numeral 46. Attached to the insulating plate by means of a rivet or eyelet 47 is the spring 48 and cooperating backing and reinforcing portion 49. The spring 48 and reinforcing member 49 as well as the terminal 50 are formed of one piece of stock having also projections such as indicated by the numeral 51 for engaging corresponding holes in the insulating plate 46 in order to prevent rotation of the spring on the insulating plate 46 around the eyelet 4'7 as center.. The front portion 48 of the spring is slightly curved and slotted, providing a pair of parallel sharp edges for the engagement of the stud 52 which projects through a corresponding guide hole in the insulating base 46. The curved portion 48 of the spring extends into the path of the stud 52. When the stud is inserted, it will engage the edges in the slotted portion 48 and will tend to flex the spring back. The function of the reinforcing portion 49 will offer increasing resistance against the flexing back of the spring.

In the modification shown in Figure 8 I have changed the reinforcing or backing spring portion of the contact. I have shown in this figure an insulating base designated by the numeral 53. Attached to this insulating base by means of a rivet or eyelet 54 is a contact comprising a base portion, a curved contact portion 55 and a reinforcing portion 56. The usual projections such as 57 for preventing the rotation of the contact on the insulating base are also provided, and the terminal 58 may also be integral with the spring and angularly rising from its base as shown. The curved portion 55 of the spring extends again into the path of the stud such as 59, and when this stud is inserted through the corresponding guide hole in the insulating base 53, it will engage the sharp edges in the slot provided in the curved front portion 55 of the contact and will tend to carry the curved portion 55 back. The reinforcing or backing portion 56 will now come into play and ofier an increasing resistance to the force with which the contact portion 55 is deflected by the stud 59.

The above described examples with reference to Figures 7 and 8 will show that it is possible to give difierent expression to the underlying idea of providing a flexible spring and a resilient back.- ing or reinforcing spring member which offers increasing resistance to the movement of the spring portion of the contact when the same is deflected by the engagement of a cooperating contact stud. Numerous other modifications may be devised.

With reference to the embodiment of the novel contact as shown in Figure 6 which was described in detail previously, this contact and cooperating backing spring may be formed of two parts instead of one. In other words, the contact part and the backing part of the spring may be formed separately and the two may be assembled on the insulating plate as an operating unit. This particular way of constructing the contact is shown in Figure 9.

Referring now to Figure 9, it will be seen that I have shown a side elevation of the modified contact completely assembled and attached to an insulating base which is shown partially in cross section. The view of the assembly shown in Figure 9 corresponds to the view of previous embodiments as shown for example in the Figures 3, 7

and 8. The resilient contact spring has a curved front portion 61 provided with a slot. Projections such as 63 extend from the base 62 of the contact into corresponding holes in the insulating base 60 for preventing rotation of the contact around the rivet or eyelet 64 which holds the spring assembly in engagement with the insulating plate. A terminal such as 65 slants angularly from the back portion of the spring. The curved portion of. the spring designated by the numeral 61 extends into the path of the stud which may be projected through the guide hole 66 indicated in dotted lines in the insulating base 60. Disposed underneath the base 82 of the spring is the resilient backing spring 67 which has two sides such as 68 rising in parallel adjacent to the sides of the base 62 of the contact spring. The front ends of the sides 68 are curved in back of the contact spring 61 and form wings as was discussed in connec tion with the embodiment of the invention shown in Figure 6. These curved wings are indicated in Figure 9 by the numeral 69. The function of this assembly is substantially the same as was described in connection with a previous embodiment and need not be repeated here.

In Figures 10 and 11 I have shown a side and a plan view, respectively, of the resilient backing or reinforcing spring used in conjunction with the embodiment shown in Figure 9. I have applied the same reference numerals to the backing spring as used in Figure 9. Accordingly, this backing spring has a base 6'7, provided with a hole 70 for attachment to the insulating base by means of a rivet or an eyelet, as discussed. Rising laterally from this base 67 are the sides 63 and 71. The

front ends of the sides are curved toward each other as is indicated at 69 and 72.

The backing spring is mounted as is shown in Figure 9, and, when the curved contact spring portion such as 61 shown in Figure 9 iscarried back during the insertion of the stud, the wings 69 and 72 will be deflected until the ends abut and form an arch as was already discussed previously. A further carrying back due to the force exerted upon the contact spring-by the insertion of the stud the arch will be spread and will oifer an increasing resistance to the displacement of the contact spring. This increasing resistance will contribute towwd establishing a firm and reliable contact between the stud and the contact spring.

In Figures 12 and I3 I have shown a plan and a side view, respectively, of the contact spring employed in connection with the assembly shown in Figure 9. The same reference numerals have been applied in Figures 12 and 13 and refer to corresponding parts shown in Figure 9. Accordingly, the reference numeral 62 designates the base portion of the contact spring provided with a hole 73 for attachment of the base portion to the insulating plate. The curved portion of the spring is designated by the reference numeral 61. This curved portion is provided with the usual slot 74 having sharp edges for engaging the surface of the stud. Numeral 65 designates the terminal which may be tinned for attaching the connecting wire through the holes 75 and 76.

While I have shown certain embodiments of my invention, I have done so by way of example only as there are many other modifications possible which can be made by one skilled in the art without departing from the teachings of the invention. The four prong socket shown is for example only, as a five or more prong socket can be built within the teachings of my invention. Five prong sockets are in common use with modern alternating current vacuum tubes, and I am not, therefore, to be limited to the four prong socket shown.

I intend to exploit and .to use the invention-in all such embodiments as may fall within the limits of the appended claims, in which I have expressed what I believe-is new and distinguishing over the art.

I' claim:

1. A contact spring, comprising a base portion for attachment to a support, a slotted free portion providing a pair of substantially parallel contact edges, backing means comprising two wings rising from said base portion and extending edgewise towards said free portion, the ends of said wings being curved toward each other and disposed in back .of said slotted portion to reinforce the pressure which said edges may exert upon a cooperating contact stud.

2. A contact spring, comprising a fiat base portion for rigid attachment to a support, a terminal portion extending from said base portion, a slotted contact portion extending from said base, said slotted contact portion providing a pair of substantially parallel edges for engaging the surface of a cylindrical contactstud substantially in lines of pressure along the sides of said stud, backing means for said slotted portion comprising plate like wing members extending from the sides of said base and having forwardly extending tips curved toward each other, said curved tips being disposed back of said contact portion for reinforcing said portion.

tion for rigid attachment to a support, a terminal portion extending from said base portion, a slotted contact portion extending from said base, said slotted contact portion providing a pair of substantially parallel edges for engaging the surface of a cylindrical contact stud substantially in lines of pressure along the sides of saidstud, backing means for said slotted portion comprising plate like wing members extending from the sides of said base and having forwardly extending tips curved toward each other, said curved tips being caused to abut by the progressive engagement of said contact portion therewith for reinforcing said contact portion.

3. A contact spring, comprising a fiat base por- 4. A contact spring, comprising aflat base portion for rigid attachment to a support, a termi nal portion extending from said base portion, a slotted contact portion extending from said base, said slotted contact portion providing a pair of substantially parallel edges for engaging the surface of a cylindrical contact stud substantially in lines of pressure along the sides of said stud, backing means for said slotted portion comprising plate like wing members extending from the sides of said base and having forwardly extending tips curved toward each other, said curved tips being caused to abut responsive to being progressively engaged by said contact portion toreinforce said portion, and said wings being caused to spread apart responsive to the application of pressure upon said abutting tips for increasing said reinforcing action thereof.

5. A contact for attachment to a support having an opening for guiding a contact stud therethrough, said contact comprising a resilient contact portion disposed in the path of said stud and adapted to be displaced thereby, and means for reinforcing the action of said contact portion with progressively increasing pressure responsive to the displacement of said contact portion by said stud, said means comprising a backing member disposed substantially centrally 'of said contact portion in back thereof and having res'lient wings curved toward each other, said wings being adapted to be engaged by said contact portion and deflected thereby during the displacement thereof. I

6. In combination with a resilient contact adapted to be slidingly engaged by a contact stud and to establish contact with the surface of said stud in a linesubstantially parallel to the axis of said stud, backing means for progressivelyreinforcing the pressure of said contact, said backing means comprising a pair of resilient wings curved toward each other and forming an open contact in a direction substantially transversally to the axis of said stud, said backing means comprising a pair of resilient wings curved toward .each other and forming an open arch in back of said contact.

8. Contact making means, comprising a substantially cylindrical stud, guide means for positioning said stud, resilient contact means for engaging the surface of said stud in a line substantially parallel to the axis of said stud, said contact means being disposed in the path of said stud and deflected thereby angularly to the axis of said stud upon positioning .of said stud, and yielding reinforcing means for said contact means adapted to be engaged thereby and deflected sub stantially transversally to the axis of said stud,

said reinforcing means comprising two resilient spring means cooperating with each other and with said contact means for applying progressively increasing reinforcing pressure to the back of said contact means.

GEORGE PEARSON. 

